The present invention relates to a shielded electrical connector and, more particularly, to a hermaphroditic electrical connector for mating with a complementary hermaphroditic electrical connector. More specifically, the invention relates to an electrical connector of this type which incorporates means for shunting alternate electrical contacts when the connector is unmated with another connector.
With the ever increasing use of data communications equipment, there is a growing need for electrical connectors for terminating electrical cables and for connecting data equipment, or components thereof, to each other. Electrical connectors of the type used for data communications equipment are disclosed, for example, in the U.S. Pat. Nos. 4,449,778 and 4,501,459 (reissued as U.S. Pat. No. Re. 32,760). These connectors comprise an insulating terminal housing formed of a base member and a cover member and having a front mating face for connection to a complementary connector and a rear wire-connecting face for connection to an electrical cable. A parallel row of four electrical terminals is mounted on a terminal supporting platform that extends between the front and rear faces of the housing. These terminals are configured at one end to mechanically and electrically connect to an insulated wire and configured at the other end to contact another, like terminal, for example of a complementary electrical connector. Each terminal comprises a resilient contact tongue spaced from the terminal supporting platform and having a free end extending away from the mating face. Each contact tongue is matable against a corresponding contact tongue of the complementary connector to urge the contact tongues toward the respective platforms from which they are supported.
The aforementioned U.S. Pat. Nos. 4,449,778 and 4,501,459 also teach the provision of means for shunting alternate electrical contacts when the connector is unmated with another, complementary connector. This shunting, or interconnection of the open contacts prevents spurious electrical signals, such as may occur by misconnection or from static electricity, from harming the attached computer equipment.
The shunting is effected by two "shunting bars" which bridge the electrical contact terminals to be shunted. One shunting bar connects the first and third contacts together while the other shunting bar connects the second and fourth contacts together. When the connector is mated with another, complementary connector, the electrical contact tongues are forced away from the shunting bars, thus breaking the shunt circuits.
The U.S. Pat. No. 4,682,836, discloses a similar connector arrangement wherein the shunting bars are replaced by shunting wires which have a "C" shaped configuration. The shunting bars and the shunting wires are arranged in parallel, side by side, perpendicular to the contact terminals. As a result of this tandem arrangement, one shunting bar or wire contacts two of the contact tongues at a different, relative location than the other. In particular, the contact points of two of the contact tongues are nearer the tongues' free ends than the other. Since the tongues contact the respective shunting bars or wires at an angle, two of the contact tongues are depressed to a greater extent by the shunting bars or wires than the other two contact tongues. Over a long period of use, the resilient characteristics of two contact terminals vary with respect to the other two so that, over time, the connector becomes less reliable.
An additional problem with the known arrangements for shunting the contacts is the minimal contact area provided by the shunting bars or shunting wires. The bars and wires make essentially a point contact with the contact tongues so that the resistance at the point of contact is unnecessarily high.
Finally, the assembly of the known connectors by the user is unnecessarily complicated. Such connectors are normally furnished as a "bag of parts" which require knowledge and skill to assemble in the field. For example, the connector disclosed in the U.S. Pat. No. 4,501,459, mentioned above, requires that the two shunting bars be separately mounted into the housing before the housing is assembled together and closed by the cover. Similarly, in the case of the connector disclosed in the U.S. Pat. No. 4,682,836, mentioned above, the U-shaped shunting wires must be inserted in a holding block, and this block must then be attached to the contact holder which, in turn, is inserted in the housing. Particularly since the connector parts are small and easily dropped or lost in the field, such assembly is less than satisfactory.